Conventionally, as is known, timber has been widely used as the material for vehicle parts such as flooring, walls and roofing. However, in recent years, regulation of the felling of tropical and subtropical forests has been strengthened from the perspective of environmental protection, and the use of timber even for vehicle parts is also becoming difficult. In addition, with regard to transportation vehicles such as trucks, buses, railway rolling stock, freight containers and the like, in response to recent improvements in transportation and to the strengthening of legal regulations, increases in load capacity are demanded, and, in particular, with regard to trucks, in the 1994 revision of the Road Traffic Act in Japan, controls on overloading were strengthened, and increases in load capacity by means of weight reduction of vehicle materials are pressing.
As a result, in recent years, an aluminum honeycomb panel and the like have become used in large quantities in vehicle materials with the goal of weight reduction and increased rigidity. However, an aluminum honeycomb panel not only increase costs, but it is difficult to cut to the desired size, and there is the processing problem that, as it is, it cannot be held to the frame using screws, therefore, it is not coming into wide use as material which replaces timber.
In addition, when used as a flooring material for vehicles, an aluminum honeycomb panel is weak with regard to concentrated loads; when a load is concentrated on a small area, that area becomes dented, and therefore, it is unable to withstand practical use.
For this reason, the use of resin foams, which are sometimes called synthetic woods as flooring for vehicles has also been proposed. These are reinforced and their rigidity increased by glass fibers within the resin foam, however, this is not sufficient, and to cover the lack in rigidity, they are generally made thicker. For this reason, even though the specific weight of the resin foam itself is low, by weight per unit of area, the weight reduction is not always sufficient. In addition, the hardness of the surface of resin foams is low and this is unfavorable from the point of view of durability. There is also a problem with properties for fixation by screws such that screws are not very effective at holding the resin foams to a frame during installation.
An objective of the present invention is the development of a flooring material for vehicles which eliminates these problems, is superior in its light weight properties, rigidity, and impact resistance, and is superior in its cutting processability such that it can be freely cut into members of desired size and in its properties for fixation by screw such that it can be held in place by screws.